Tack stitches are used so often in
temari making that they deserve some attention. Technically, a tack
stitch is simply kagari. However, the orientation of
it based on need is just as important as the actual stitch size. When
used to hold threads in place such as described here, it can also be
known as tabane kagari.

Tack stitches are used to hold
centers and other intersections in place on divisions and markings. As
such, they should be as unobtrusive as possible. This is accomplished
through use of a tiny stitch size, and tight placement at the
intersection of the marking line. Notice in the example below (granted,
this is worked in highly contrasting thread for demonstration purposes)
that the tacking thread is brought up tightly in the corner of the
intersection of the marking lines. It is then carried diagonally over
the intersection, so that an equal number of marking lines are on either
side of it. This assures that the intersection of the marking threads
will be tight and secure (do not confuse tight with pulling the tacking
thread tight. Normal tension is still
used), and clean without disturbing the lay of the threads.

Normally tacking is done with the
same thread as what is being anchored; that is, marking threads are
tacked with the same thread used to mark the ball. However, some people
will use a piece of regular sewing thread, or a single strand of floss
as tacking thread. The smaller size makes for an even more invisible
anchor. This is especially notable if the marking thread is of a large
gauge; tacking with the same thread can create a noticeable lump.

The tack stitch is taken into the
mari; it's not just passing under the marking or stitching threads and
gathering them into a crisp center. That is one half of its purpose. The
other half and perhaps more important is to hold that intersection point
accurately and securely on the mari (especially in the case of division
threads), without impacting the placement of the center.

Tack stitches also play an
important role in matsuba kagari. In
order to achieve the star burst effect so often desired, a distinct
center is needed. This is achieved by tacking the center intersection.
Care should always be taken to be sure that an equal number of stitching
threads are on either side of the stitch; this is what gives clear
resolution to the center, and avoids skewing the appearance of the reach
of the stitch.